Seismic performance of full-scale reinforced concrete columns

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Abstract

The deformation capacity of a concrete column can be expressed by using
different ductility parameters such as curvature ductility, displacement ductility or drift
capacity. However, little research has been conducted into the relationship among
different ductility parameters. The objectives of this research are (1) to investigate the
relationship among various ductility parameters by considering the effects of shear spanto-depth
ratio and axial load level and (2) to develop methods and procedures that can be
used to estimate the deformation capacity of reinforced concrete columns.
Five full-scale reinforced concrete columns were tested at The University of
Texas at Austin. Test results indicated that the shear span-to-depth ratio and axial load
level were important parameters influencing the relationship among various ductility
parameters. Measured plastic hinge lengths of column specimens were also affected by
the shear span-to-depth ratio and axial load.
The plastic hinge length of concrete columns was investigated by studying the
compressive strain profile of the core concrete. An analytical procedure was used to study
the effect of various parameters on plastic hinge length. Based on the results of the
experiments and a parametric study, a new expression that can be used to estimate plastic
hinge lengths was proposed.
Two methods that can be used to predict the deformation capacity of reinforced
concrete columns were developed. One of these methods can be considered as a state-ofthe-art
analytical method, which employs various phenomenological models for
confinement of concrete, reinforcing bar buckling, reinforcing bar slip and shear
deformations. The other method consists of simple expressions derived by studying the
lateral load response of columns as influenced by the P-Δ effect. The use of the rigorous
analytical method provided reasonably accurate estimates for the deformation capacity of
over one hundred columns tested by various researchers. The use of simple expressions,
on the other hand, traced the lower-bound of the measured drift capacities of these
columns. The simple expression is recommended for use in performance-based design of
reinforced concrete columns.